When it is desired to cut brush, bushes, small trees and other vegetation at ground level to clear land, the typical equipment used is a self-propelled, power driven riding tractor with a rotary cutter assembly positioned either forwardly or rearwardly of the tractor. The rotary cutter assembly is moved along a cutting path to engage the vegetation to be cut.
One such prior art brush cutter machine is the skid steer tractor on which the operator rides and which includes the engine that propels the driving wheels of the tractor, and a cutter assembly positioned out front of the tractor. The cutter assembly is supported from the ground by caster wheels, and the cutter assembly is pivotally connected to the tractor about a longitudinal axis. With this arrangement, the cutter assembly and its cutter deck and cutter blades can tilt about the longitudinal axis with respect to the tractor so as to adjust for the variations in the terrain. The skid steer brush cutter of this type is found to be desirable because of its relatively low center of gravity that avoids the tipping over of the vehicle, because the cutter assembly is in front of the tractor and can be aggressively controlled by the operator, because it is rugged and adaptable to the variable terrain where this type of cutting is required, and because the front caster wheels do not require a steering linkage which would be vulnerable to damage from impact with objects in the cutting path.
The prior art skid-steer brush cutters typically have two or three rectilinear rotary cutting blades supported beneath a cutter deck and a motor and belt driving system which rotates the blades in the same direction of rotation. This tends to urge the cut vegetation out to the side of the brush cutter, where it is out of the way of the advancing vehicle. Some of the mowers are rear discharge mowers which urge the cut vegetation through the mower cutter deck without cutting the vegetation into small pieces. The rear discharge mowers utilize baffles to help direct the cut vegetation rearwardly around the blades and through the deck.
Another type brush cutter is the rotary drum cutter which has rotary drums mounted in front of the tractor with the rotating drums having their axes oriented parallel to the ground. Chippers are mounted to the face of the drum that chop up trees and brush. The chippers chop the vegetation into chips as the chippers pass over the vegetation. These are slower than rotary cutters and run slowly over trees to allow the chipper to produce an effective result.
The prior art also teaches a cutter assembly with one or more rotary cutters mounted with horizontal discs attached to the vertical shaft. Each cutter disc has relatively small cutter blades hingedly attached to the extremity of the disc with bolts. The cutter blades usually are attached with a single bolt to allow pivoting of the cutter blade when objects are hit. However, the small cutter blades also can be rigidly attached with multiple bolts. Also, these machines do not mulch very well because the discs usually do not propel the cut vegetation through the deck where it can be re-cut, as can be done by rectilinear blades. The disc cutters do not mulch well because of the discs occupying the space where mulching occurs.
The ends of the blades of both disc cutters and rectilinear blade cutters normally extend beyond the front of the cutter deck so that they are freer to cut down brush and small trees before the brush, etc. is engaged by the cutter deck. The blades typically cut near the base of the vegetation. In this design the tall vegetation tends to fall primarily toward the machine and on top of the cutter deck where the material cannot be mulched. This poses some inconvenience and possibly a hazard to the driver of the tractor and to the machine. Also, the blades tend to propel the cut brush laterally away from the on-coming cutter assembly where it cannot be mulched. In some instances, this requires the driver to back the tractor up and run over the previously cut brush, trees, etc. so as to cut them apart in smaller pieces, generally known as "mulching."
The large brush and other large vegetation cut by both the rectilinear blades and the disc blades of the prior art brush cutters is likely to be left in large pieces on the ground. Therefore, once the prior art brush cutters and their cutter assemblies have moved through a field and have cut brush and other vegetation growing in the field, usually it is desirable to have the brush cutter move back through the field so as to recut or mulch the previously cut brush, limbs, etc. Obviously, this second pass through the field requires more operator time and machine time and more fuel, and results in increased wear on the equipment and does not adequately mulch.
Further, in most of the typical prior art cutter assemblies, the cutter blades all rotate in the same direction, which tends to urge the cut brush, trees, etc. out to the side of the implement, thus removing the cut brush etc. out of the cutting path, which may be desirable in some instances so that the equipment can move faster through a field, but which retards the ability of the cutter assembly to re-cut or mulch the vegetation.
Another aspect of the prior art is the caster arm and assembly configuration. It would be desirable to be able to rapidly change the height of the cutter deck and cutter blades from the ground so that the cutting height of the rotary cutter blades would be changed to be at the correct height for cutting of smaller brush or larger brush and young trees, etc. The prior art design of casters for front mounted rotary cutters is to have the casters attached to a vertical axle and with the vertical axle mounted in a housing to allow the caster axle to rotate but to keep it in the same position relative to the machine. The height of the cutter deck is adjusted by putting spacers either over or under the housing about the axle, thereby raising or lowering the caster with respect to the cutter deck. This is used as an inexpensive way of adjusting the height of the cutter deck. However, when the caster axle is lowered to lower the wheel and raise the cutter deck, the axle extends farther out of its housing and becomes more vulnerable to bending. This trait is acceptable for mowers but not in a brush cutter application in which the brush cutter is used more aggressively to cut heavier brush, small trees, etc. When the upright axle of the caster wheel becomes bent or otherwise damaged, it is likely that the cutting operation of the brush cutter will have to be terminated and the caster wheel replaced.
Thus, it can be seen that it would be desirable to have a brush cutter suitable for cutting and mulching brush, small trees and other mid-sized vegetation which, after cutting the vegetation away from the ground surface, mulches the vegetation so that it is rendered into small particles suitable for rapid deterioration. To induce mulching of the brush, it would be desirable to cause the vegetation to be urged to fall toward the cutting path in front of the brush cutter as the lower portion of the vegetation is cut, so that the cutter assembly passes over the cut vegetation and re-cuts or mulches the vegetation without requiring the vehicle to be driven back over the initially cut vegetation. Further, it can be seen that it would be desirable to have adjustable height caster wheels for supporting the cutter deck which are heavy duty so as to withstand the rugged conditions normally encountered by such a brush cutter, and which are able to raise or lower the wheels with respect to the cutter deck to effectively lower or raise the cutter deck with respect to the ground surface, without requiring the placement of shims, etc. about the vertical shaft of the caster wheels.